Electron-discharge tube



J 1952 A. J. w. M. VAN OVERBEEK ,6

ELECTRON-DISCHARGE TUBE Filed Oct. 5, 1950 uun vi il" INVENTOR- ADRIANUS J.W.M. VAN OVER'BEEK AGENT Patented June 10, 1952 ELECTRON-DISCHARGE TUBE Adrianus Johannes Wilhelmus Marie van Overbeek, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application October 5, 1950, Serial No. 188,558 In the Netherlands October 28, 1949 2 Claims. 1

This invention relates to electron-discharge tubes, wherein a ribbon-shaped electron beam is produced.

In such a tube the electron gun usually consists of a cage-shaped chamber which is formed by a number of plate-shaped electrodes and in which an elongated cathode is arranged preferably in the plane of one of the walls. Opposite the cathode an accelerating anode is provided, which is furnished with a slit extending parallel to the longitudinal direction of the cathode.

For various purposes, for example, telephone selectors, distributors, counting devices, mixer tubes and the like, the electron gun is required to satisfy stringent requirements. Thus, for example, a ribbon-shaped beam carrying a maximum current at a minimum voltage is required to be produced. On the other hand the surface of the anode system struck by the beam should be very small and not be influenced by small discrepancies in the construction of the gun or by small voltage variations of the electrodes havin a fixed potential. Moreover, the ribbonshaped beam should have cleanly outlined side faces, and the construction of the gun should be such that no secondary electrons issue therefrom, by which an excessive deflection anode current, which is different for difierent specimens, would be caused. However, guns of known construction exhibit certain imperfections which are hardly tolerable for the aforesaid uses and the reasons for which are not obvious.

Elaborate tests have now been made and a construction devised by which the aforesaid requirements are satisfied to a higher degree.

According to the invention, an electron-discharge tube comprising an electron gun which produces a ribbon-shaped beam and consists of a cage formed by plate-shaped electrodes and containing an elongated cathode arranged in the plane of one of the walls of the cage, an accelerating electrode arranged opposite the cathode being furnished with a slit-shaped aperture, is characterized in that a plurality of rods is provided, within the cage between the accelcrating electrode and the cathode and arranged symmetrically with respect to the said slit such that the distance of each of the rods from the accelerating electrode is at the most of the distance from the accelerating electrode to the cathode, the distance of each of the rods from the remaining plate-shaped electrodes corresponding at least to the distance from each rod to the nearer edge of the slit provided in the accelerating electrode. A low voltage, preferably zero potential, is applied to the rods so that they may be connected to the cathode. It has been found that the spacing should be such that when the tube is in use the voltage applied to the accelerating electrode is elfective in the spaces between the rods and between the rods and the cathode.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, given by way of example, in which a cross section of an electron-discharge tube is shown, with an electron gun according to the invention, comprising a cathode I, a shielding electrode 2, control electrodes 3, 3 for adjusting the beam current, focussing electrodes 4, 4 and an accelerating electrode 5. Two rods 8, and 8' are provided at the cathode side of the accelerating electrode 5 so that the distance of these rods from the edges 9, 9 of a slit 6 provided in the electrode 5 is equal to or smaller than the distance of the rods 8, 8' from the other electrodes, more particularly the electrodes 4, 4'. The distance from the rods 8, 8' to the accelerating electrode 5 is required to be smaller than of the distance from the accelerating electrode 5 to the cathode I. At the exterior of the gun, the beam is adapted to be deflected by deflection plates 1, 1' to anodes in the usual manner. When the tube is in use the voltage applied to the accelerating electrode 5 should be such that the field due to this voltage is effective in the spaces between the rods 8, 8' and between the electrodes 4, 4 e. g. 300 volts. The electrodes 2, 4, 4, 8, 8 may be connected to the cathode, thus obtaining a so-called one-voltage gun, of which only the accelerating electrode 5 is supplied with positive voltage. The deflection of the beam to anode ID or H) can be obtained by applying a control-voltage on the deflection plate varying from till 220 volts, the plate 1' being connected to a constant voltage of 150. The focussing action of the electrodes 3, 3' can be adjusted by means of the low negative voltages derived from the potentiometer l l WhatIclaim is:

1. An electron-discharge tube comprising an electron-gun which produces a ribbon-shaped beam, said electron gun comprising a cage having walls constituted by a set of plate-shaped electrodes and an elongated cathode mounted in the plane of one of the walls of the cage, an accelerating electrode mounted opposite the cathode, said accelerating electrode having a slit-shaped aperture, a plurality of rods mounted within the cage between the accelerating electrode and the cathode and arranged symmetrically with respect to the said slit, each of said rods being spaced from the accelerating electrode a distance which is at most 5- /3 o'f the' dis tance from the accelerating electrode to the cathode, the distance of each of the rods from the remaining plate-shaped electrodes corresponding at least to the distance iremeach rod to the nearer edge of the slit provided in the accelerating electrode.

2. An electron-discharge "tribe as claimed in claim 1, in which the rods are connected to the cathode in an electrically conductive manner.

ADRIANUS JOHANN'ES WILHELMUS MARIE VAN OV'ERBEEK.

*fi FE Nfii fi I -E "Ih'e foll'oiili'n'g references are of "record in the file of this patent:

UNITED STATES PATENTS flmnber Name Date 2,472,319 -S; elg-in June 7, 1949 2f,5;1'1;14 3 Adler June 13, 1950 25391250 *Hoseman Jan. 23, 1951 

